Velocity modulation impulse generator



June 18, 1946. uss 2,402,364

VELOCITY MODULATION IMPULSE GENERATOR Filed July 17, 1941 F IGA.

l l I 17 I 1 i- 16 20 mmuw h. O I F I62.

IN VEN TOR ffoai r A. 5065 BY ATTORNEY Patented June 18, 1946 VELOCITY MODULATION IMPULSE GENERATOR Robert R. Buss, Palo Alto, Calif., assignor to International Standard Electric Corporation, New York, N.-Y., a corporation of Delaware Application July 17, 1941, Serial No. 402,733

' charge tube for both the generation of a cathode current pulse and its conversion by velocity modulation into pulses of radio frequency energy.

According to one feature of the invention in an arrangement for the generation of short pulses of radio frequency energy, comprising an electron discharge tube provided with means for the generation of ultra-high frequency waves by electron velocity modulation, the cathode, a control electrode and a. further electrode in the tube are connected in .an external circuit to constitute a blocking oscillator so that the electron current is caused to fiow in short pulses. The further electrode, which functions as an anode for the blocking oscillator, may be constituted by an accelerator electrode which is also employed to focus the electron beam, or if desired a separate electrode may be provided in the tube.

Other objects and features of my invention will be apparent from the following detailed description thereof made in connection with the accompanying drawing in which:

Fig. 1 is'a schematic circuit diagram showing a pulse generator according to my invention, and

Fig. 2 is a further schematic circuit diagram of a modified arrangement in which a separate anode is employed in the blocking oscillator portion of the tube.

Like reference numerals are used in the two figures for indicating like parts.

Referring first to Fig. 1, the tube I consists of a velocity modulated tube comprising a cathode 2, control electrode 3, accelerating electrode 4, resonant chamber grouping circuit 5, resonant chamber extracting circuit 6 and collector electrod I. The construction of velocity modulated tubes of this general kind is well-known. Reference may be had, for example, to copending application Serial No, 353,042 filed August 17, 1940.

Electrons from the cathode 2 are formed into a beam by the accelerating electrode 4; which is at 7 Claims. (Cl. 315-6) a high positive potential with respect to the oath. ode, and pass through grids 8 and 9 of the resonant chamber 5, drift tube I and grids I I and I2 of the resonant chamber 6 to the collector electrode I. The resonant chamber circuits and 6 are tuned to the ultra-high frequency at which the tube i desired to generate oscillations, and feedback between these circuits is provided by the conductor I3. The grouping circuit 5 serves to modify the velocity of the electrons in the beam, and due to their changes in velocity the electrons become bunched in the drift tube I0. Energy is extracted from the bunched electrons by the circuit 6 and an output is taken by a coupling loop I to a work circuit, for example, an antenna I5.

charged, accelerator electrode current will begin.

to flow and due to the positive reaction provided by the transformer I6 this current will increase continuously and rapidly to a value near saturation. The voltage at the accelerator electrode l will thus decrease and the voltage of the control electrode 3 will increase in a positive sense and 85 will cause .a large cathode current to flow. The

' increase in accelerator electrode current will cease when this current approaches the saturation current of the cathode. At this time the voltage of the control electrode 3 will begin to decrease 40 causing a rapid decrease in accelerator electrode 4!! become negative.

During the period when cathode current is flowing the condenser I8 is charged and due to this charge the control electrode is held negative. The condenser I8 will, however, slowly discharge through the resistance I1, until when accelerator electrode current again starts toflow, the cycle will be repeated after a period determined by the time constant of the resistance-condenser com-' bination I1, I 8,

It will be seen that the control electrode 3 ac- Since the potential of the accelerator electrode 4 varies, this may have an undesirable effect upon the iocussing of the electron beam. As shown in Fig. 2, the potential of the accelerator electrode A may be held constant by inserting a high resistance 2! in the high tension lead to this electrode and connecting a by-pass condenser 22 between it and the cathode 2. In this case it will be necessaryto provide in the neighborhood of the control electrode 3 an additional electrode 23 connected to a point positive with respect to said cathode to function as an anode for the blocking oscillator portion of the tube.

It will be appreciated that the circuits described are simple and efilcient and call for minimum power requirements since no load is effective except that actually required for the pulses. Moreover the problem of building up an adequately short voltage pulse from a short current pulse as in arrangements proposed heretofore does not arise.

What is claimed is:

l. A circuit arrangement for the generation of short pulses of radio frequency energy comprising an electron discharge tube having an electron emitting cathode, a control electrode, a further electrode adjacent said control electrode connected to a source of positive potential with respect to said cathode, means for forming electrons emitted from said cathode into a beam, means for modifying the velocity of electrons in said beam, drift means for allowing electrons in said beam to become grouped after modification of their velocity, means for extracting energy from said grouped electrons, and means external of said tube for connecting together said cathode, control electrode and further electrode to constitute a blocking oscillator whereby the electron current is caused to flow in short pulses.

2,.A circuit arrangement according to claim 1, wherein an accelerating electrode is provided in said tube for focussing said emitted electrons into a beam, and comprising a lead from said focussing electrode to a point on said sourceof potential which is positive with respect to said cathode, a resistance in said lead and a condenser connected between said accelerator electrode and said cathode.

3. A circuit arrangement according to claim 1 wherein said means external of said tube comprises a circuit between said control electrode and said cathode and a circuit between said further electrode and said cathode, a condenser shunted by a resistance in said first-mentioned circuit and a coupling for producing positive reaction between said second-mentioned and said first-mentioned circuits.

4. A circuit arrangement according to claim 1 wherein said means external of said tube comprises an auto-transformer and a sourceof high potential, 9. connection including said source from one end of said auto-transformer to said further electrode, a connection from the other end of said auto-transformer to said control electrode, a condenser shunted by a leak resistance, a connection from one side of said condenser to said cathode and a connection from the other side of said condenser to a tapping on said auto-transformer intermediate its ends.

5. A circuit arrangement for the generation of short pulses of radio frequency energy comprising an electron discharge tube having an electron emitting cathode, a control electrode, an accelerating electrode connected to a source of positive potential with respect to said cathode for forming electrons emitted from said cathode into a beam, means for modifying the velocity of electrons in said beam, drift means for allowing electrons in said beam to become grouped after modification of their velocity, means for extracting energy from said grouped electrons, and means external of said tube connecting to ther said cathode control electrode and accelerating electrode to constitute a blocking oscillator whereby the electron current is caused to flow in short pulses.

6. A circuit arrangement for the generation of short pulses of radio frequency energy comprising an electron discharge tube having an electron emitting cathode, a control electrode, an accelerating electrode for focussing emitted electrons into a beam, a first apertured resonant chamber for modifying the velocity of electrons in s id beam, a drift tube for allowing electrons in said beam to become rouped in their transit therethrough, a second apertured resonant chamber for extracting energy from said grouped electrons, and means external of said tube for connecting together said cathode, control electrode and accelerating electrode to constitute a blocking oscillator whereby the electron current is caused to flow in short pulses and short pulses of radio frequency energy are generated in said second apertured resonant chamber.

'7. A circuit arrangement for the generation of short pulses of radio frequency energy comprising an electron discharge tube having an electron emitting cathode, a control electrode, a further electrode adjacent said control electrode con-' nected to a source of positive potential with respect to said cathode, means for forming electrons emitted from said cathode into a beam, a first-apertured resonant chamber for modifying the velocity of electrons in said beam, a drift tube for allowing electrons in said beam to become grouped in their transit therethrough, a second apertured resonant chamber for extracting energy from said grouped electrons, and a circuit exter nal of said tube for connecting together said oath ode, control electrode and said further electrode to constitute a blocking oscillator.

ROBERT R. BUSS. 

